[LLVMdev] Getting the target information of a branch instruction

[abhi232 at cc.gatech.edu]

Hello all,

The algorithm that i am trying to implement has this particular line that
says

if variable p gets a value at statement u
{
}

If i want to find out whether a particular variable gets a value at a
statement how can i do that.

Do i just need to check whether the getOperand(0) returns a non zero value
or is there any other way?

Please suggest something..
thankz in advance..






> Thanks a lot for the help guys..
> I will try to get the information on these lines...
>
> Thank you once again...
> Will bug you guys after some time now.  :)
>
>> I think you can refer to lib/VMCore/AsmWriter.cpp for these things.
>>
>> E.g.,
>> You can use 'if(I.isTerminator())' if a instruction 'I' is terminator.
>> You can use 'if (isa<BranchInst>(I))' if a instruction 'I' is 'br'
>> instruction.
>> and so on...
>>
>> Thx,
>> Seung Jae Lee
>>
>> ---- Original message ----
>>>Date: Mon, 2 Jul 2007 17:15:00 -0400 (EDT)
>>>From: abhi232 at cc.gatech.edu
>>>Subject: Re: [LLVMdev] Getting the target information of a branch
>>> instruction
>>>To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
>>>
>>>> On Mon, 2 Jul 2007 abhi232 at cc.gatech.edu wrote:
>>>>> Hello all,
>>>>> I am new to the llvm infrastructure so if this question is already
>>>>> resolved please redirect me to that link.
>>>>>
>>>>> I am writing a pass for flow sensitive and context sensitive alias
>>>>> analysis.for that i require the previous and next instruction of all
>>>>> the
>>>>> instructions.Is there an intrinsic that can help me getting the
>>>>> instruction numbers directly because i read at the llvm.org website
>>>>> making
>>>>> changes to instruction class may be lead to unstableness..Also if i
>>>>> have
>>>>> a
>>>>> branch instruction how do i get he target of the branch
>>>>> instruction.All
>>>>> i
>>>>> could find was machine independent target code.
>>>>
>>>> Is this in the code generator, or in the LLVM IR?   I assume that you
>>>> mean
>>>> the LLVM IR.  Given an unconditional branch, you can use
>>>> I->getOperand(0)
>>>> to get the destination.  You should check out this document, it
>>>> describes
>>>> lots of interesting stuff:
>>>> http://llvm.org/docs/ProgrammersManual.html
>>>>
>>>> in particular:
>>>> http://llvm.org/docs/ProgrammersManual.html#common
>>>>
>>>> -Chris
>>>>
>>>> --
>>>> http://nondot.org/sabre/
>>>> http://llvm.org/
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>>
>>>
>>>Thanks a lot for the information.Actually i am looking for the target of
>>>conditional branch operation something like
>>>
>>>some instruction INST...
>>>if(condition)
>>>{
>>>}
>>>else
>>>{
>>>}..
>>>
>>>In this case the next set for the instruction INST will consist of the
>>>code in the true condition as well as the falses condition....
>>>for that i am checking if the opcode is terminator and after that i am
>>>getting the opcode name and if it is a branch instruction then i should
>>>get the statement number of the branch...i am using a map to associate
>>> an
>>>instruction with number...i had a look at the IR and it has inserted
>>>cond_true,cond_false and cond_next labels in the IR of the bytecode...
>>>
>>>How do i go further with these values in hand?
>>>please guide on this topic.
>>>Thanks a lot.
>>>abhinav.
>>>_______________________________________________
>>>LLVM Developers mailing list
>>>LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>>http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>